| Summary: | 碩士 === 銘傳大學 === 生物科技學系碩士班 === 102 === Abstract：
Bacteriocins are antibiotic substances that are produced by bacteria that are active against other bacteria. W. hellenica 4-7, isolated from the traditional Taiwanese fermented food sian-sianzih (fermented clams), was previously found to produce a bacteriocin active against Listeria monocytogenes and some other Gram-positive bacteria. Bacteriocin activity decreased slightly after autoclaving (121°C for 15 min), but was inactivated by protease K and trypsin. Mass spectrometry analysis revealed the bacteriocin mass to be approximately 3205.6 Da. N-terminal amino acid sequencing yielded a partial sequence, NH2- KGFLSWASKATSWLVGP, by Edman degradation. The obtained partial sequence showed high homology with leucocin B-TA33a; however, at least two different residues were observed. No identical peptide or protein was found, and this peptide was therefore considered to be a novel bacteriocin produced by W. hellenica 4-7, and termed weissellicin L.
Abstract：
A total of 102 LAB were isolated from three different coffee farms in Taiwan. These isolates were classified and identified by restriction fragment length polymorphism analysis and sequencing of 16S ribosomal DNA、rpoA and pheS genes. Heterofermentative Leuconostoc and Weissella species were the most common LAB found in two farms located at an approximate altitude of 800 m. Lactococcus lactis subsp. lactis was the most common LAB found in the remaining farm, located at an approximate altitude of 1200 m. It is therefore suggested that the altitude and climate may affect the distribution of LAB. On the basis of phylogenetic analysis, two strains included in the genera Enterococcus were considered as two potential novel species or subspecies. In addition, a total of 34 isolates showed antifungal activity against Aspergillus flavus. Moreover, 7 Lactococcus lactis subsp. lactis and 1 Enterococcus faecalis strains were found to have bacteriocin-like inhibitory substance (BLIS) -producing capability. These results suggest that various LAB are associated with fresh coffee cherries in Taiwan. Some of the isolates found in this study showed potential as antifungal agents.
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